1. Field of the Invention
The present invention relates to a process for blending liquid rubber and carbon black with a high torque mixer, which is a mixer for highly viscous material, without the use of special apparatus such as a roller mill to easily give a composition of carbon black and liquid rubber in which the carbon black is uniformly dispersed.
2. Description of the Prior Art
The reinforcing effect of carbon black on liquid rubber is substantial as well as on conventional synthetic rubbers. Carbon black can be effectively combined with liquid rubber as a reinforcing filler. Further, it is very difficult to uniformly disperse carbon black in liquid rubber with a simple mixer such as a high torque type mixer except by using a special apparatus which involves complicated operations or special operations. The desired reinforcing effect of the filler in the rubber cannot be obtained without a uniform dispersing operation.
The known methods of blending carbon black with a liquid rubber to form a uniform dispersion include the use of a paint roller mill (three roller mill), a mill, and a special continuous mixer (manufactured by RAPRA). However, in order to uniformly blend and disperse the filler and rubber, it is necessary to pass the mixture through the apparatus many times and large size apparatus for practical industrial use have not been commercialized. When carbon black is blended with a viscous liquid such as liquid rubber, it is necessary to crush the carbon black in the blend because carbon black is usually obtained as beads so that grinding type apparatus have been required.
It has been reported that the dispersibility of carbon black in liquid rubber is poor even when the components are blended for a long time in a conventional mixer for viscous liquids such as high speed mixers for bread powder, mixers having Z-type blades, transfer mixers, corn mixers and the like. [Journal of Nippon Rubber Associate, Vol. 45 No. 3 (1972) Pages 54-62 and Rubber Digest, Vol. 25 No. 10 (1973) Pages 19-24].
A method of blending has also been proposed in which carbon black is blended with the liquid rubber in a wet master batch system wherein the liquid rubber is contacted and mixed with a dispersion of carbon black in water under suitable conditions to give a granular dispersion and then the granules are dried and diluted with the liquid rubber. The method is excellent for mass production, but is not suitable for small scale production in long production lines. A need therefore continues to exist for a method of simply and uniformly blending carbon black in liquid rubber.